Influence of Sr⁺² concentrations on growth of SrTiO₃ thin films synthesized by hydrothermal–galvanic couple method

This work aims to explore the effects of Sr⁺² concentrations on the growth of SrTiO₃ thin films synthesized by the hydrothermal–galvanic couple method. The syntheses were conducted on the TiN/Si substrates in 2 M NaOH solutions consisting of various Sr⁺² concentrations at 80 °C. Cubic SrTiO₃ films were formed at Sr⁺² concentrations above 0.0004 M. Epitaxial-like growth of the SrTiO₃ films was found over the TiN underlayer at such various Sr⁺² concentrations. The relative diffraction peak intensity, the grain size, and the thickness of the obtained SrTiO₃ films first increased rapidly, then reached the maximum, and decreased gradually afterwards with increasing the Sr⁺² concentrations. The grain size and the thickness of the films would reach the maximum at 0.001 M [Sr⁺²]. Nanograins of the films were present at high Sr⁺² concentrations. The growth kinetics of the films was determined by a modified Avrami–Erofe'ev equation. Nucleation governs the formation of SrTiO₃ at high Sr⁺² concentrations, leading to the nanograins. Grain growth predominates at low Sr⁺² concentrations, yielding the large grains. Moreover, both the dielectric constant and the dielectric loss of the obtained SrTiO₃ films increased with decreasing the Sr⁺² concentrations. - Highlights: • Cubic SrTiO₃ films were synthesized by a hydrothermal–galvanic couple method. • Surface morphology of SrTiO₃ films was tailored by varying the Sr⁺² concentrations. • Epitaxial-like SrTiO₃ films grown over TiN underlayers • Growth kinetics of SrTiO₃ described by a modified Avrami-Erofe'ev equation • Dielectric properties of the SrTiO₃ films were determined